LCDs have a number of advantages, including their lighter weight, reduced thickness and smaller power dissipation, over other kinds of display devices, and have been used as not only a display device with a small screen such as the monitor of a cellphone but also the big screen of a TV set. In color LCDs that are used extensively today, one pixel consists of three subpixels representing the three primary colors of light, namely, red (R), green (G) and blue (B), and the color difference between those colors red, green and blue is typically made by color filters.
In general, in order to expand a color reproduction range, the concentration of a pigment in a color filter is increased. However, the higher the concentration of a pigment, the lower the transmittance of its color filter layer, thus making it impossible to achieve a high luminance.
Recently, display devices that add four or more primary colors together have been proposed (see Patent Documents Nos. 1 to 3, for example) as a replacement for an ordinary display device that uses the three primary colors. Such a display device that uses four or more primary colors is sometimes called a “multi-primary-color display device”. A multi-primary-color display device could expand the color reproduction range relatively easily.